Polymers provide tremendous benefits to society. Their use can be seen almost everywhere, from materials used in space, water, automobiles, electronics, households, and medicine to name a few areas. Polymer products can be lightweight, hard, strong, and flexible and have distinct thermal, electrical, and optical characteristics. Accordingly, polymer systems garner a tremendous amount of research and development. Scientists continue to develop polymer systems with improved properties. One of the challenges facing these scientists is how to precisely control the rheological properties of polymers, which are critical for many manufacturing processes. Another challenge is the development of improved methods for repairing and restoring an area of a material that has been damaged.
Organogels have been a topic of concentrated research over the past several years. Organogels use organic solvents as the swelling agent as opposed to a “hydrogel” in which the swelling agent is water. Proposed applications for organogels include their use as viscosity modifiers, drug delivery systems, and electrical cable insulators (see EP 2254127 A1). For example, one paper showed organogels consisting of reversible covalently bonded polymers in various organic solvents (Deng et al., Macromolecules 2010-43(3):1191-1194). However, such systems are typically singular in composition, having only one polymerization reaction with a single trigger. The organogels also typically possess mechanical properties that are too soft for structural applications.
Traditional polymer cure cycles are generally characterized by a single transition from a liquid state to a rigid state, which limits processing capabilities. Multiple component and multiple stage polymers have been described for the benefit of obtaining the properties of several components within a single system (see EP0003652 B1, and U.S. Pat. No. 4,096,202 (Farnham et al.), U.S. Pat. No. 4,886,851 (Ikenaga et al.), and U.S. Pat. No. 7,857,447 (Myung et al.)). Acrylate systems have been of particular interest due to the economic and industrial importance of poly(acrylate) polymers. Traditional methods based on multiple component and multiple stage systems generally require direct engineering control of the system to obtain the desired composition and structure. In some cases, polymers are synthesized independently and then blended together. Traditional polymer cure cycles have been tailored to possess different cure rates based on the alteration of the kinetics of the polymerization. However, the range of control is usually dictated by the reaction temperature. The polymerization proceeds in a singular fashion from a liquid of a designed viscosity to a solid of a designed modulus.
Additional challenges presented by traditional polymeric materials are the processing limitations caused by the polymer's high viscosity and its susceptibility to oxygen inhibition. Rapidly reacting systems, such as commercially available epoxy resins (e.g., Devcon 5 Minute® epoxy), possess relatively high viscosities of about 10,000 centipoise (cps). Lower viscosity (about 60 cps) epoxy resin systems exist, but react very slowly at room temperature and usually require curing at temperatures of 70° C. for 8 or more hours. Traditional acrylate resins can be characterized by much lower viscosities, but generally suffer from oxygen inhibition during free radical polymerization. Several techniques have been suggested to help counteract this problem. However, the techniques involve the use of new initiating systems (see U.S. Publication No. 2006/0062922 (Xu et al.)), implementation of oxygen scavengers, and incorporation of thiol monomers.
Accordingly, there is a need for improving the rheological and mechanical properties of polymer materials, particularly, for the restoration of large damage volumes, defects, or other spaces in polymers. There is also a need for improved polymer systems that can easily and efficiently repair and restore (regenerate) impaired areas of a material. These needs are met by the polymer systems and methods described herein.